Changing hemostatic management in post-partum hemorrhage.

Early and fast assessment of hemostasis during postpartum hemorrhage (PPH) is essential to allow early characterization of coagulopathy, estimate bleeding severity and improve outcome. During PPH, fibrinogen decrease occurs earlier than other coagulation factors deficiency and hypofibrinogenemia is an early marker of PPH severity of progression. With good evidence in the context of PPH, point-of-care viscoelastic (VET) hemostatic assays have been shown to provide rapid assessment of hemostatic disorders, low fibrinogen levels, and allow VET-guided fibrinogen replacement. Further studies are needed to define the thresholds for the other coagulation parameters.

Analgesia Nociception Index-Guided Remifentanil versus Standard Care during Propofol Anesthesia: A Randomized Controlled Trial.

The clinical benefits to be expected from intraoperative nociception monitors are currently under investigation. Among these devices, the Analgesia Nociception-Index (ANI) has shown promising results under sevoflurane anesthesia. Our study investigated ANI-guided remifentanil administration under propofol anesthesia. We hypothesized that ANI guidance would result in reduced remifentanil consumption compared with standard management. This prospective, randomized, controlled, single-blinded, bi-centric study included women undergoing elective gynecologic surgery under target-controlled infusion of propofol and remifentanil. Patients were randomly assigned to an ANI or Standard group. In the ANI group, remifentanil target concentration was adjusted by 0.5 ng mL-1 steps every 5 min according to the ANI value. In the Standard group, remifentanil was managed according to standard practice. Our primary objective was to compare remifentanil consumption between the groups. Our secondary objectives were to compare the quality of anesthesia, postoperative analgesia and the incidence of chronic pain. Eighty patients were included. Remifentanil consumption was lower in the ANI group: 4.4 (3.3; 5.7) vs. 5.8 (4.9; 7.1) µg kg-1 h-1 (difference = -1.4 (95% CI, -2.6 to -0.2), p = 0.0026). Propofol consumption was not different between the groups. Postoperative pain scores were low in both groups. There was no difference in morphine consumption 24 h after surgery. The proportion of patients reporting pain 3 months after surgery was 18.8% in the ANI group and 30.8% in the Standard group (difference = -12.0 (95% CI, -32.2 to 9.2)). ANI guidance resulted in lower remifentanil consumption compared with standard practice under propofol anesthesia. There was no difference in short- or long-term postoperative analgesia.

Relationship between pre-incision Pupillary Pain Index and post-incision heart rate and pupillary diameter variation in children.

BACKGROUND: The Pupillary Pain Index is a recent pupillometric index designed to assess the level of analgesia under general anesthesia in children and adults. If analgesia is inadequate, acute nociceptive stimuli such as skin incision may induce significant hemodynamic disturbances. AIMS: Our aim was to investigate the potential relationship between pre-incision Pupillary Pain Index and heart rate increase following skin incision in children. METHODS: This was a prospective, non-randomized, registered pilot study. We included children undergoing surgery under general anesthesia. Pupillary Pain Index was assessed 2 min before skin incision. Then, heart rate maximal variation (ΔHR ) and pupillary diameter maximal variation (ΔPD ) in the minute following incision were recorded. Spearman coefficient was calculated to characterize the relationship between Pupillary Pain Index and ΔHR or ΔPD . Using receiver operating characteristic curve analysis, we also studied the predictive value of pre-incision Pupillary Pain Index for heart rate and pupillary diameter reactivity. RESULTS: 53 patients were included (10 ± 4 years, 40 ± 19 kg). There was a modest correlation between pre-incision Pupillary Pain Index and ΔHR (Spearman rs = 0.35 [0.05-0.57], p = .011), and between pre-incision Pupillary Pain Index and ΔPD (Spearman rs = 0.54 [0.33-0.71], p < .001). Regarding the predictive value of Pupillary Pain Index for heart rate or pupillary diameter reactivity, the corresponding areas under the receiver operating characteristic curves were 0.90 [0.82-0.99] and 0.78 [0.65-0.93], respectively. A threshold of Pupillary Pain Index <3 predicted the absence of heart rate reactivity at incision with a good performance (negative predictive value = 1). CONCLUSIONS: In children, pre-incision Pupillary Pain Index was moderately correlated with post-incision nociception. Pre-incision Pupillary Pain Index had good predictive performances for heart rate or pupillary diameter reactivity to skin incision. Pre-incision Pupillary Pain Index <3 might predict the absence of heart rate reaction to incision.

Impact of Lacticaseibacillus rhamnosus GG on the Emulsion Stability of Raw Milk.

Lactic acid bacteria (LAB) have been studied for several decades to understand and determine their mechanism and interaction within the matrix into which they are introduced. This study aimed to determine the spatial distribution of Lacticaseibacillus rhamnosus GG (LGG) in a dairy matrix and to decipher its behaviour towards milk components, especially fat globules. Two strains of this widely studied bacterium with expected probiotic effects were used: LGG WT with pili on the cell surface and its pili-depleted mutant-LGG ΔspaCBA-in order to determine the involvement of these filamentous proteins. In this work, it was shown that LGG ΔspaCBA was able to limit creaming with a greater impact than the wild-type counterpart. Moreover, confocal imaging evidenced a preferential microbial distribution as aggregates for LGG WT, while the pili-depleted strain tended to be homogenously distributed and found as individual chains. The observed differences in creaming are attributed to the indirect implication of SpaCBA pili. Indeed, the bacteria-to-bacteria interaction surpassed the bacteria-to-matrix interaction, reducing the bacterial surface exposed to raw milk. Conversely, LGG ΔspaCBA may form a physical barrier responsible for preventing milk fat globules from rising to the surface.

Management of severe thermal burns in the acute phase in adults and children.

OBJECTIVES: To provide recommendations to facilitate the management of severe thermal burns during the acute phase in adults and children. DESIGN: A committee of 20 experts was asked to produce recommendations in six fields of burn management, namely, (1) assessment, admission to specialised burns centres, and telemedicine; (2) haemodynamic management; (3) airway management and smoke inhalation; (4) anaesthesia and analgesia; (5) burn wound treatments; and (6) other treatments. At the start of the recommendation-formulation process, a formal conflict-of-interest policy was developed and enforced throughout the process. The entire process was conducted independently of any industry funding. The experts drew up a list of questions that were formulated according to the PICO model (Population, Intervention, Comparison, and Outcomes). Two bibliography experts per field analysed the literature published from January 2000 onwards using predefined keywords according to PRISMA recommendations. The quality of data from the selected literature was assessed using GRADE® methodology. Due to the current paucity of sufficiently powered studies regarding hard outcomes (i.e. mortality), the recommendations are based on expert opinion. RESULTS: The SFAR guidelines panel generated 24 statements regarding the management of acute burn injuries in adults and children. After two scoring rounds and one amendment, strong agreement was reached for all recommendations. CONCLUSION: Substantial agreement was reached among a large cohort of experts regarding numerous strong recommendations to optimise the management of acute burn injuries in adults and children.

Effect of Different Concentrations of Propofol Used as a Sole Anesthetic on Pupillary Diameter: A Randomized Trial.

BACKGROUND: Pupillometry monitoring under general anesthesia is based on the assumption that pupillary diameter variations reflect the adequacy of the provided analgesia to the intensity of the nociceptive surgical stimulus. The accurate interpretation of pupillometric data requires establishing clearly what the expected baseline unstimulated pupillary diameter at each specific level of hypnosis is. Opioids decrease pupillary diameter in a dose-dependent fashion. In contrast, the effects of hypnotic drugs on pupillary diameter are not well known. Our aim was to describe the potential relationship between propofol predicted effect-site concentrations (Cets) ranging from 1 to 3 µg/mL and pupillary diameter. METHODS: Patients were randomized to receive propofol by target-controlled infusion at a predicted Cet of 1, 2, or 3 µg/mL (groups P1, P2, and P3, respectively). Pupillary diameter measurements were performed after 10 minutes of steady-state propofol infusion at the randomized Cet. No stimulation was performed during the study. Heart rate and bispectral index (BIS) were continuously recorded. RESULTS: Forty patients were included: (13, 14, and 13 in groups P1, P2, and P3, respectively). Mean pupillary diameter was 5.7 mm (1 mm) in group P1, 4.8 mm (1.3 mm) in group P2, and 3.3 mm (0.8 mm) in group P3. Propofol had a dose-dependent effect on pupillary diameter (linear regression R = 0.45, P < .001). Pupillary diameter was positively correlated with the BIS (Spearman r = 0.75 [95% confidence interval (CI), 0.54 to -0.87] P < .001). CONCLUSIONS: From 1 to 3 µg/mL of predicted Cet, propofol has a dose-dependent effect on pupillary diameter. Within this concentrations range, there is a positive correlation between BIS and pupillary diameter. The subcortical effect of propofol on pupillary diameter is correlated to its effect on the cortex. Studies assessing pupillary diameter as a marker of the nociception-antinociception balance should be performed in patients with a standardized depth of hypnosis.

Assessment of Coagulation by Thromboelastography During Ongoing Postpartum Hemorrhage: A Retrospective Cohort Analysis.

BACKGROUND: Rapid assessment of hemostasis during postpartum hemorrhage (PPH) is essential to allow characterization of coagulopathy, to estimate bleeding severity, and to improve outcome. Point of care (POC) coagulation monitors could be of great interest for early diagnosis and treatment of coagulation disorders in PPH. METHODS: Women with ongoing PPH >500 mL who clinically required an assessment of coagulation with thromboelastography (TEG) were included. The primary aim of this retrospective observational cohort study was to assess the predictive accuracy of TEG parameters for the diagnosis of coagulation disorders (hypofibrinogenemia ≤2 g/L, thrombocytopenia ≤80,000/mm, prothrombin ratio ≤50%, or activated partial thromboplastin time ratio ≥1.5) during PPH. The analyzed TEG parameters were Kaolin-maximum amplitude (K-MA), Kaolin-maximum rate of thrombus generation using G (K-MRTGG), functional fibrinogen-maximum amplitude (FF-MA), and functional fibrinogen-maximum rate of thrombus generation using G (FF-MRTGG). Secondary aims of this study were (1) comparison of the time delay between classical parameters and velocity curve-derived parameters (K-MA versus K-MRTGG and FF-MA versus FF-MRTGG) and (2) evaluation of the accuracy of TEG parameters to predict severe hemorrhage estimated by calculated blood losses. RESULTS: Ninety-eight patients were included with 98 simultaneous TEG analyses and laboratory assays. All parameters had an excellent predictive performance. For the Kaolin assay, no significant difference was evidenced between K-MA and K-MRTGG for the predictive performance for hypofibrinogenemia ≤2 g/L and/or thrombocytopenia ≤80,000/mm (respective area under the curve [AUC], 0.970 vs 0.981). For the functional fibrinogen assay, no significant difference was evidenced between FF-MA and FF-MRTGG for the predictive performance for hypofibrinogenemia ≤2 g/L (respective AUC, 0.988 vs 0.974). For both assays, the time to obtain results was shorter for the velocity parameters (K-MRTGG: 7.7 minutes [2.4 minutes] versus K-MA: 24.7 minutes [4.2 minutes], P < .001; FF-MRTGG: 2.7 minutes [2.7 minutes] versus FF-MA: 14.0 minutes [4.3 minutes], P < .001). All TEG parameters derived from the Kaolin and functional fibrinogen assays and Clauss fibrinogen were significantly predictive of severe PPH >2500 mL. CONCLUSIONS: During PPH, when coagulation assessment is indicated, TEG provides a rapid and reliable detection of hypofibrinogenemia ≤2 g/L and/or thrombocytopenia ≤80,000/mm. No difference in performance was evidenced between the velocity-derived parameters (K-MRTGG and FF-MRTGG) and the classical parameters (K-MA and FF-MA). However, velocity-derived parameters offer the advantage of a shorter time to obtain results: FF-MRTGG parameter is available within ≤5 minutes. POC assessment of hemostasis during PPH management may help physicians to diagnose clotting disorders and to provide appropriate hemostatic support.

EEG profiles during general anesthesia in children: A comparative study between sevoflurane and propofol.

BACKGROUND: In this prospective study, we describe the electroencephalographic (EEG) profiles in children anesthetized with sevoflurane or propofol. METHODS: Seventy-three subjects (11 years, range 5-18) were included and randomly assigned to two groups according to the anesthetic agent. Anesthesia was performed by target-controlled infusion of propofol (group P) or by sevoflurane inhalation (group S). Steady-state periods were performed at a fixed randomized concentration between 2, 3, 4, 5, and 6 µg.ml-1 of propofol in group P and between 1, 2, 3, 4, and 5% of sevoflurane in group S. Remifentanil was continuously administered throughout the study. Clinical data, Bispectral Index (BIS), and raw EEG were continuously recorded. The relationship between BIS and anesthetic concentrations was studied using nonlinear regression. For all steady-state periods, EEG traces were reviewed to assess the presence of epileptoid signs, and spectral analysis of raw EEG was performed. RESULTS: Under propofol, BIS decreased monotonically and EEG slowed down as concentrations increased from 2 to 6 µg.ml-1 . Under sevoflurane, BIS decreased from 0% to 4% and paradoxically rose from 4% to 5% of expired concentration: this increase in BIS was associated with the occurrence of fast oscillations and epileptoid signs on the EEG trace. Propofol was associated with more delta waves and burst suppression periods compared to sevoflurane. CONCLUSION: Under deep anesthesia, the BIS and electroencephalographic profiles differ between propofol and sevoflurane. For high concentrations of sevoflurane, an elevated BIS value may be interpreted as a sign of epileptoid patterns or EEG fast oscillations rather than an insufficient depth of hypnosis.

Pupillary Pain Index Changes After a Standardized Bolus of Alfentanil Under Sevoflurane Anesthesia: First Evaluation of a New Pupillometric Index to Assess the Level of Analgesia During General Anesthesia.

BACKGROUND: The pupillary pain index (PPI) is a novel pupillometric index, designed to assess intraoperative analgesia. It is based on the evaluation of the pupillary response to electrical stimuli of increasing intensity. It ranges from 1 (low level of pupillary reactivity, high level of analgesia) to 10 (high level of pupillary reactivity, low level of analgesia). In this first evaluation of the PPI, our objective was to investigate the PPI changes after a bolus of 10 µg·kg(-1) of alfentanil in children under sevoflurane general anesthesia. METHODS: After ethics committee approval and informed consent, 20 healthy children (9 ± 5 years) undergoing elective surgery under general anesthesia were included in this prospective, open, registered pilot study (NCT02646592). Anesthetic induction was standardized with sevoflurane 6% and propofol 1 mg·kg(-1). After tracheal intubation, sevoflurane concentration was maintained at 2% for 10 minutes. A first PPI measurement was performed (PPI-1), and a bolus of 10 µg·kg(-1) was administered. Two minutes after this bolus, a second PPI measurement was performed (PPI-2). Heart rate, blood pressure, and bispectral index were recorded before and after each PPI measurement. Resting pupillary diameter was recorded before each PPI measurement. PPI scores before and after the bolus of alfentanil were compared using a Wilcoxon signed rank test. RESULTS: PPI scores decreased after administration of a bolus of alfentanil (median difference: -3 [95% confidence interval, -4 to -2]). The median (quartiles) of PPI-1 (baseline, before alfentanil) was 6 (4, 7), and the median (quartiles) of PPI-2 (after alfentanil) was 2 (2, 3) (P < .001). No difference was found in resting pupillary diameter before PPI-1 and PPI-2 (2.2 ± 0.2 and 2.2 ± 0.3 mm, respectively; P = .86). There were no significant changes in heart rate or blood pressure after PPI measurements (P = .46 and .49, respectively). Bispectral index was slightly increased after PPI measurements (P = .01; mean bispectral index increase <5%). No withdrawal movements occurred during PPI measurements. CONCLUSIONS: There was a significant decrease in PPI after alfentanil administration. The results of this pilot study suggest that PPI score decreases when the level of analgesia increases. PPI measurement was not associated with a clinical or hemodynamic nociceptive response. This new index might provide useful information to individually adapt opioid administration before nociceptive stimuli under general anesthesia.

Influence of Depth of Hypnosis on Pupillary Reactivity to a Standardized Tetanic Stimulus in Patients Under Propofol-Remifentanil Target-Controlled Infusion: A Crossover Randomized Pilot Study.

BACKGROUND: Pupillometry allows the measurement of pupillary diameter variations in response to nociceptive stimuli. This technique has been used to monitor the balance between analgesia and nociception. Under general anesthesia, the amplitude of pupillary dilation is related to the amount of administered opioids. The objective of this study was to determine whether at a constant infusion rate of opioids, the pupillary response was influenced by depth of hypnosis assessed by the bispectral index (BIS). METHODS: Twelve patients (14-20 years) anesthetized for orthopedic surgery were included. Under propofol-remifentanil target-controlled infusion, remifentanil effect site target concentration was fixed at 1 ng/mL. Two measures of pupillary reflex dilation were performed on each patient in a randomized order: one at BIS 55 and one at BIS 25. These levels of BIS were obtained by adjusting propofol target concentration and maintained for 10 minutes before each measure. For each measure, we applied a standardized tetanic stimulation on the patient's forearm (60 mA, 100 Hz, 5 seconds). All measures were performed before the beginning of surgery. RESULTS: Pupillary dilation was significantly greater at BIS 55 than at BIS 25: 32.1% ± 5.3% vs 10.4% ± 2.5% (mean difference estimate [95% confidence interval]: 21.8% [12.9-30.6], P < .001), without carryover effect (P = .30) nor period effect (P = .52). Hemodynamic parameters and BIS were not modified by the stimulation. CONCLUSIONS: In patients receiving a constant infusion of remifentanil at a target concentration of 1 ng/mL, pupillary dilation after a standardized tetanic stimulation was influenced by depth of hypnosis assessed by the BIS.

Pupillary reflex dilation in response to incremental nociceptive stimuli in patients receiving intravenous ketamine.

Pupillometry is a non-invasive monitoring technique, which allows dynamic pupillary diameter measurement by an infrared camera. Pupillary diameter increases in response to nociceptive stimuli. In patients anesthetized with propofol or volatile agents, the magnitude of this pupillary dilation is related to the intensity of the stimulus. Pupillary response to nociceptive stimuli has never been studied under ketamine anesthesia. Our objective was to describe pupillary reflex dilation after calibrated tetanic stimulations in patients receiving intravenous ketamine. After written consent, 24 patients of our pediatric burn care unit were included. They received an oral morphine premedication (0.3 mg kg-1) 1 h before their scheduled daily dressing change. Just before the procedure, they received 1 mg kg-1 of intravenous ketamine. Two minutes after this bolus, tetanic stimulations of incremental intensities were performed on the arm of each patient (5-10-20-30-40-60 mA, 60 s interval between stimulations). Pupillary diameter, heart rate and movements were recorded before and after each stimulation. Tetanic stimulations were associated with changes in pupillary diameter and heart rate. The magnitude of these changes was significantly influenced by the intensity of stimulation (ANOVA for repeated measures, p < 0.001). Movement was associated with a 32% increase in diameter (ROC curves, AUC 0.758) with 65% sensitivity and 77% specificity. In children, pupillary reflex dilation to nociceptive stimuli persists under deep sedation obtained with 1 mg kg-1 of intravenous ketamine combined with a 0.3 mg kg-1 oral morphine premedication, and its magnitude depends on the intensity of the stimulation. Our results confirm that pupillometry could be a relevant way to monitor nociception in anaesthetised subjects, including those receiving ketamine. Trial registration clinicaltrials.gov, NCT 02648412.

Pupillometry-guided Intraoperative Remifentanil Administration versus Standard Practice Influences Opioid Use: A Randomized Study.

BACKGROUND: Pupillometry has shown promising results for assessing nociception in anesthetized patients. However, its benefits in clinical practice are not demonstrated. The aim of this prospective randomized study was to evaluate the impact of intraoperative pupillometry monitoring on perioperative opioid consumption in major gynecologic surgery. METHODS: After receiving ethics committee approval and written consent of patients, American Society of Anesthesiologists status I to II women undergoing gynecologic surgery were included in this single-blinded, prospective, parallel-arm randomized study. General anesthesia was standardized with propofol-remifentanil target-controlled infusion. Patients were randomly assigned into two groups. In the pupillometry group, remifentanil administration was guided by pupillary diameter changes. In the standard group, remifentanil administration was left to the discretion of the anesthesiologist. The primary outcome was intraoperative remifentanil consumption. RESULTS: Fifty-five patients were analyzed. Remifentanil consumption was markedly decreased in the pupillometry group (3.8 [3.4 to 4.8 µg · kg · h] vs. 7.9 µg · kg · h [6.5 to 9.0 µg · kg · h] in the standard group; difference = 4.2 µg · kg · h [95% CI, 3.0 to 5.3 µg · kg · h]; P < 0.001). Cumulative 0- to 12-h morphine consumption was reduced in the pupillometry group (two-way repeated measures ANOVA 0.3 ± 0.1 vs. 0.4 ± 0.2 mg/kg; P = 0.048). A telephone survey 3 months after surgery revealed that 15 of 29 patients in the standard group still experienced procedure-related pain versus 3 of 23 in the pupillometry group (chi-square P = 0.037). No adverse events associated with pupillometry were observed during the study. CONCLUSIONS: The use of pupillometry to guide intraoperative analgesia reduced intraoperative remifentanil consumption and postoperative morphine requirements. The possible consequences of decreasing intraoperative remifentanil in terms of chronic pain require further investigation.

Comparison of MSC properties in two different hydrogels. Impact of mechanical properties.

Once articular cartilage is damaged, it has poor ability to heal. At present, alginate-based hydrogels have 3D-dimensional physical structures with great potential for applications in carilage tissue engineering. For osteochondral defect, it will be necessary to use stratified scaffold to mimic zonal organization of cartilage. This study aims to compare the characteristics of alginate (Alg)/hyaluronic acid (HA) hydrogels which will mimic cartilage with alginate (Alg)/hydroxyapatite (Hap) hydrogels which will mimic subchondral bone. In this work, we fabricated the 3D-Alg/HA and Alg/Hap hydrogel scaffolds by the original spraying method. From the physical-mechanical properties, we compared mechanical behaviour of Alg/HA and Alg/Hap hydrogel scaffolds, which were examined using indentation testing and viscosity behaviour. This results showed that the Alg/Hap hydrogels exhibited a relative high mechanical strength, as well as the viscosity of Alg/Hap hydrogels is slight slower than Alg/HA hydrogels. However, autoclaving has more deleterious effect on the mechanical and viscosity properties of Alg/HA and Alg/Hap hydrogels. Cytotoxicity was evaluated through the culture of hydrogel beads-laden Wharton's jelly mesenchymal stem cells (WJ-MSC). In addition, the chondrogenic differentiation of WJ-MSC encapsulated into Alg/HA and Alg/Hap hydrogels were performed by histological analyzing during 30 days of culture. From these results, the percentage of living cells for Alg/Hap is significantly higher than Alg/HA, which also is associated with the results of shear viscosity. Both of hydrogels exhibited differentiate into chondrocyte matrix as collagen and proteoglycans. In conclusion, Alg/Hap hydrogels presented better mechanical property, cytocompatibility and differentiation characteristics than Alg/HA hydrogels.

Is there a cause-and-effect relationship between physicochemical properties and cell behavior of alginate-based hydrogel obtained after sterilization?

Alginate-based hydrogel scaffolds are widely used in the field of cartilage regeneration and repair. If the effect of autoclaving on the alginate powder is well known, it is not the same for the possible effects of the sterilization UV treatment on the properties of the hydrogel after polymerization. To select an effective sterilization treatment of alginate-based materials, one must find what are inter-relationship between the characteristics (chemical, physical and mechanical) of alginate-based hydrogel during sterilization, and what consequences have affected on cell behavior. In this study, we investigated the influence of UV sterilization treatments (UV-1 and UV-2: 25 and 50min, respectively) and autoclaving to obtain alginate (Alg)/hyaluronic acid (HA) hydrogel, as well as further evaluated the relationship between physicochemical properties and cell behavior of Alg/HA hydrogel after UVs and autoclaving. The physicochemical properties of this mixture at the powder or polymerized states were analyzed using ATR-FTIR, HPLC-SEC, rheological, indentation testing and sterility testing. The cell behaviors of hydrogels were evaluated by cell viability and proliferation, and chondrogenic differentiation. The effects of treatment parameters and their correlation with the others characteristics were determined statistically by Principal Component Analysis (PCA). In this study, we have shown that the cell behavior in alginate-based hydrogels was not only regulated by physicochemical properties (as molar mass or/and viscosity), but also associated with the controlling of sterilization time. It can provide a basis for choosing an effective method of sterilization, which can keep the mechanical or physical-chemical properties of Alg-based hydrogel scaffold and maintain its cytocompatibility and its ability to induce chondrogenesis from mesenchymal stem cells.

Bulk and local rheology in a dense and vibrated granular suspension.

In this paper, we investigate experimentally the dynamics of particles in dense granular suspensions when both shear and external vibrations are applied. We study in detail how vibrations affect particle reorganization at the local scale and modify the apparent rheology. The nonlocal nature of the rheology when no vibrations are applied is evidenced, in agreement with previous numerical studies from the literature. It is also shown that vibrations induce structural reorganizations, which tend to homogenize the system and cancel the nonlocal properties.

Granular avalanches down inclined and vibrated planes.

In this article, we study granular avalanches when external mechanical vibrations are applied. We identify conditions of flow arrest and compare with the ones classically observed for nonvibrating granular flows down inclines [Phys. Fluids 11, 542 (1999)PHFLE61070-663110.1063/1.869928]. We propose an empirical law to describe the thickness of the deposits with the inclination angle and the vibration intensity. The link between the surface velocity and the depth of the flow highlights a competition between gravity and vibrations induced flows. We identify two distinct regimes: (a) gravity-driven flows at large angles where vibrations do not modify dynamical properties but the deposits (scaling laws in this regime are in agreement with the literature for nonvibrating granular flows) and (b) vibrations-driven flows at small angles where no flow is possible without applied vibrations (in this last regime, the flow behavior can be properly described by a vibration induced activated process). We show, in this study, that granular flows down inclined planes can be finely tuned by external mechanical vibrations.

Bispectral index under propofol anesthesia in children: a comparative randomized study between TIVA and TCI.

BACKGROUND: In children, only a few studies have compared different modes of propofol infusion during a total intravenous anesthesia (TIVA) with propofol and remifentanil. The aim of this study was to compare Bispectral Index (BIS) profiles (percentage of time spent at adequate BIS values) between four modes of propofol infusion: titration of the infusion rate on clinical signs (TIVA0 ), titration of the infusion rate on the BIS (TIVABIS ), target controlled infusion (TCI) guided by the BIS either with the Kataria model (TCI KBIS ) or the Schnider model (TCI SBIS ). METHODS: Sixty-six children (aged from 4 to 14 years) were prospectively randomized into one of the four groups. In the TIVA0 group, the anesthesiologist was blinded to the BIS. In each group, the percentage of time with adequate BIS values (45-55), the bias, and imprecision were calculated. RESULTS: The propofol consumption was similar in the four groups. During the maintenance phase, the percentage of time spent in the targeted BIS range was significantly lower in the TIVA0 group compared to the three other groups (TIVA0 : 31% ± 22, TIVABIS : 59% ± 17, TCI KBIS : 53% ± 12, TCI SBIS : 56% ± 17). The bias was not statistically different between the four groups, but the imprecision was larger for the TIVA0 group. Compared to the Kataria model, the Schnider model was associated with shorter time delay to reach the desired BIS, to eyes opening, and to tracheal extubation. CONCLUSIONS: Propofol administration using manual infusion guided by clinical signs was associated with higher risks of over- or underdosage when compared to BIS-guided administrations. When propofol infusion was guided by the BIS, no major difference was found between TIVA and TCI (either with the Kataria or the Schnider model). This study highlights the need of a pharmacodynamic feedback during propofol anesthesia in children.

Drop formation in shear-thickening granular suspensions.

We study droplet formation in granular suspensions by systematically varying the volume fractions (φ) and particle diameters (d). For suspensions with water as the suspending liquid, we find three different regimes. For dilute suspensions (φ≤45%), drop formation follows the predictions for inertial breakup and exhibits identical dynamics to that of pure water. The breakup is strongly asymmetrical in this case. Only for more concentrated suspensions (φ>45%) does the presence of particles change the dynamics and two other regimes, a symmetrical inertial regime and a Bagnoldian regime, are uncovered. We construct and discuss a phase diagram that allows us to understand and predict the breakup behavior in granular suspensions.

Nonuniversality in the pinch-off of yield stress fluids: role of nonlocal rheology.

The pinch-off behavior of yield stress fluids is investigated using droplet and liquid-bridge breakup experiments. Contrary to expectations, the neck thinning behavior depends strongly on the way the breakup experiment is carried out. This nonuniversal behavior can be explained through an analysis of the thinning dynamics as well as the shapes of the fluid necks. Recent nonlocal models for the rheology of yield stress fluids are found to be compatible with the results presented.